Official Guide 11th edition

I recently ordered the Official Guide 11th edition and it was delivered to me today. The book begins with some general info on the GMAT exam and then has a Diagnostic Test. The test is paper based and has a number of questions (around 25) on each section. After the test, it has a chart which takes your score range on each section and assigns you a category - below average, average, above average and excellent. This tells you which area you need to put more emphasis on. The rest of the book has 800 questions in all from supposedly recently retired tests.

I took the Problem Solving diagnostic test and scored 17/24 which gave me a rating of 'above average.' Even though the diagnostic questions were pretty tough, 7 wrongs are concerning at this stage on Problem Solving, which I consider one of my stronger areas and rely upon to bump up my score on GMAT day. I know DS and RC are my weak spots and I will get a few wrong. Also it took me a little over an hour to do these 24 questions suggesting that my 17 right answers came at a higher average time per question than I will get on the actual GMAT.

Next, I decided to tackle some practice Problem Solving questions and did 85 questions (in about 2.5 hrs) randomly out of the 249 so that I got a mixture of easy, medium and hard questions. I got 84 of these correct. Atleast 12-15 of these 85 I have seen on the 10th edition, so there is definitely some overlap (atleast in PS) between the 10th and 11th editions contrary to what many people believe. The questions on the 11th edition were no more difficult or easy than those on the 10th edition but they are different.

So today was just 11th edition problem solving practice, did 109 questions and reviewed their solutions in about 4 hrs. Phew!